1. Field of the Invention
This invention relates to techniques for reducing road vibration in trucks such as the tractor in tractor-trailer rigs and more particularly, to a method of substantially eliminating road vibration in such trucks resulting primarily from wheel/tire runout and misalignment vibration, and for increasing the longevity of tractor tires, by the following steps: Removing the bearing slack from the truck wheels by tightening the bearings; trimming or "trueing" the tires of the drive tandem true to the axle center as the center of each tire rotational circle; utilizing a strobe light and vibration sensor to detect weight imbalances in each of the sets of trimmed wheels while the wheels are spun individually by operation of the vehicle engine when the frame is jacked; balancing the wheels by adding weight to appropriate areas of the wheel rim; setting or adjusting the wheel and axle alignment using laser beam equipment and mounting levels on the wheel alignment racks attached to the truck frame to facilitate aligning the three axles in a common plane; marking the axle hub for alignment with the valve stem on each tire to maintain the original tire mount configuration; and balancing the existing brake drums or providing balanced brake drums in the wheels.
One of the primary causes of road vibration in trucks such as tractor/trailer rigs, is wheel/tire runout, or the difference between the maximum and minimum radii of the wheels as measured from the center of wheel rotation. Whenever the geometric center of a wheel is offset from the axis of rotation, a variable radius or "runout" condition exists and this condition may cause extensive vibration as the truck or rig traverses the highway. For example, with the so-called "sensitive" trucks, even a mere 0.040 inches of runout may cause a drive tandem to bounce. A set of dual wheels that are eccentric by that amount may cause an axle oscillation cycle for each wheel revolution. The axle will then become a vibrating support for the suspension, which in turn, oscillates at a frequency determined by the wheel rotational speed. This condition is exacerbated by a tendency for newer trucks to ride on low-profile radial tires which have smaller air compartments and therefore offer considerably less vibration-cushioning capacity than high-profile tires. Accordingly, truck wheels and tires are capable of not only inducing a rough ride to the detriment of the driver, but also causing frame-bending and cab-pitching phenomena in many cases. Typically, the type of tire runout vibration which drivers consider to be most objectionable originates at the rearmost tandem axle wheel/tire positions. A random check of hundreds of randomly mounted tire/wheel assemblies determined that more than fifty percent were at least 0.040 inches out of round. This condition is sufficient to produce a cab pitch of about fifty percent in the "sensitive" vehicles.
This invention provides a method of substantially reducing and effectively substantially eliminating road vibration in trucks such as tractor/trailer rigs, in addition to substantially doubling tire life, by addressing the problems of wheel runout inherent in low profile radial tires with minimum air cushioning capacity, misalignment of wheels and other objectionable imbalanced tire conditions which develop in trucks in general and tractor/trailer rigs in particular, during the many hours of road operation.
2. Description of the Prior Art
Various techniques have been developed over the years to minimize the problem of wheel/tire runout and other conditions which contribute to road vibration, minimum tire life and accompanying distress to drivers of tractor/trailer rigs. An advanced concept such as "match-mounting" of wheels and tires is one approach which is receiving considerable attention. As the tire/wheel assembly is mounted on a truck, the out-of-roundness of the tire and wheel should cancel each other out and the amount of radial runout would be minimized, under circumstances where the high point of forced variation of the tire is aligned directly over the low point of the wheel. However, matched-mounting can only be effected on wheels that have a measurable degree of built-in non-uniformity. And in the vast majority of tire and wheel combinations, there is no such built-in non-uniformity, the non-uniformity being of a random nature. Other techniques include conventional spin balancing of and "trueing", or rounding the tires, as well as jacking and bending vehicle axles rather than jacking the frame of the vehicle, but these techniques only address part of the problem. Conventional aligning of the respective truck or tractor wheels is also effected to further minimize road vibration in trucks and tractor/trailer rigs.
U.S. Pat. No. 3,483,911, dated Dec. 16, 1969, to E. C. Miller, details a "Tire Trimming Device" which is used to remove projections from the surface of a tire. The device includes a pair of flexible, parallel, toothed inter-engaging rollers designed to grasp individual projections and remove them from the tire surface with substantially no disfigurement or distortion of the tire body. A guide device such as a roller and/or a presser foot which contacts the tire surface adjacent to the projection being removed may be used with the "Tire Trimming Device". U.S. Pat. No. 3,487,872, dated Jan. 6, 1970, to H. B. Kiedrowski, details a "Tire Trimmer" which rotatably supports a tire casing having unwanted rubber-like protrusions thereon and includes brushes for flexing the protrusions into an outstanding position and knives for cutting off the flexed protrusions as the tire casing rotates. A "Tire Tread Trimming and Trueing Apparatus" is detailed in U.S. Pat. No. 3,595,295, dated Jul. 27, 1971, to Kenneth D. Curry. The apparatus is designed to round the tread of tires to give the tread a perfect annular configuration, as well as a lateral arc. It includes a tire loading and unloading device, a tire rotating and tread-flexing device for both flexing the tire before trimming and rotating the tire during trimming and a guide apparatus for trimming the tire tread to the desired configuration. U.S. Pat. No. 3,972,362, dated Aug. 3, 1976, to Hubert J. Pace, details another tire trimming device. A knife is positioned against the direction of rotation of a tire and is skimmed over the left sidewall, the tread and the right sidewall of the rotating tire at least once to trim off the nibs. Paint is preferably sprayed on the tire sidewalls, the processed tire is ejected from the device by application of a brake apparatus and black paint may be applied to one sidewall as the white wall protector is applied to the other. U.S. Pat. No. 5,048,954, dated Sep. 17, 1991, to John Madey, et al, details a "Laser-Based Wheel Alignment System". The device includes a beam of collimated light emitted from a low-power, visible laser which is split into two generally parallel beams by a partially transmitting mirror and a series of plain front surface mirrors positioned in front and alongside the vehicle being serviced. The two beams are reflected from a set of plain mirrors attached to the rims of the wheels to be aligned. The vertical and horizontal angles of each of the wheel-mounted mirrors are set by calibrated lead-screws to cancel the angular displacement of the wheels expected when the wheels are properly aligned. The reflected beams are imaged through a large aperture beam combiner on a common viewing screen. Correct toe-in and camber settings are indicated when the laser beams reflected from the wheel-mounted mirrors overlap at the center of the viewing screen. The caster settings of the front wheels are measured by observing the angle at which the reflected spots travel across the screen when the steering wheel is turned. The system can be used to align the front wheels only, or alternatively, all four wheels simultaneously.
It is an object of this invention to provide a method of balancing and aligning truck wheels which includes the steps of elevating the rear end of the truck by lifting the truck frame; trimming or "trueing" the tires of the drive tandem to the center of each axle as the center of the respective tire rotational circle; utilizing a strobe light and vibration sensor to detect weight imbalances in each set of trimmed wheels, or "duals" when the wheels are spun in sets and balancing each of the trimmed wheels by adding weight to the areas of the wheel rim where balancing weight is needed; and setting or adjusting the wheel alignment using laser beam equipment, which includes wheel alignment racks attached to the front and rear frame and provided with levels to facilitate alignment of the wheels and the three axles in a common plane.
Another object of this invention is to provide a total alignment and vibration elimination technique for trucks, which includes the steps of tightening the bearings in each set of wheels to remove the bearing slack from the wheels; marking the axle hub for alignment with the valve stem on each tire to maintain the original tire mount configuration; determining the extent of elongation of the tires using a radial run-out gauge; coating the tire treads with paint and trueing the tires of the drive tandem to the center of each axle as the center of the respective tire rotation; strobe marking each set of tires and attaching a vibration sensor to the axle or frame of the truck and utilizing a strobe light to dynamically balance each set of tires, or "duals" while the frame of the truck is jacked, and balancing each of the trimmed wheels by adding weight to the areas on the wheel rim where balancing weight is needed; setting or adjusting the wheel and axle alignment using laser beam and equipment which includes levels mounted on the wheel alignment racks attached to the front and rear frame to facilitate alignment of the three axles in parallel, vertical planes; and providing balance brake drums on the wheels, if necessary.